The present invention relates to improved apparatus for the drawing of glass fibers and is particularly concerned with such an apparatus wherein the orifice plate of the drawing bushiing is provided with a generally planar undersurface and bulk flow gas is directed upwardly against the undersurface to achieve fiber cooling and attenuation.
The invention is specifically concerned with an improvement in the apparatus disclosed in U.S. application Ser. No. 500,303, filed Aug. 26, 1974, by Edward T. Strickland. That application discloses a method and apparatus for forming glass fibers wherein the orifice plate has a generally planar undersurface and bulk flow gas is directed upwardly against the undersurface to effect cooling and fiber attenuation.
The method and apparatus of the aforementioned application is particularly desirable in that the orifice plate employed therein does not require that nozzles extend downwardly from the orifice plate. Such nozzles are typical of the prior art and are employed to effect cooling of the fibers being drawn and to maintain the fibers in separated condition. Such nozzles have the disadvantage that they add to the complexity of the orifice plate and greatly limit the density of the orifices which can be provided in the plate. The relatively large size of the orifice plate required when nozzles are employed makes it difficult to uniformly cool the plate and, thus, difficult to draw fibers of uniform diameter. Also, such bushing assemblies require relatively great amounts of precious metal alloys, thus greatly increasing their expense.
An example of a piror art assembly wherein the orifice plate is provided by nozzles may be found in U.S. Pat. No. 3,492,104 to Glaser, granted Jan. 27, 1970. The assembly shown in that patent bears certain similarities to that of the assembly of the present invention, but is critically different therefrom in a number of respects. In particular, the orifice plate of the assembly includes nozzles or tips fixed to and extending downwardly from the orifice plate and an external support is provided centrally of the plate in a V-shaped groove formed therein.